The Diary of A Madman (Kuangren riji), Lu Xun’s first well-known short story and the alleged first modern short story in vernacular Chinese, is famous for its first-person narrative by an intellectual that is suffering from a persecution complex. As acknowledged by Lu Xun himself and argued by most scholars, this short story was influenced by Gogol’s homonymic short story, but has developed more profound melancholy and indignation. However, as my paper demonstrates, this perspective neglects the role of Japan as an intermediary in the transculturation of madness. First, Lu Xun’s initial encounter with Gogol’s Diary of A Madman was through his reading of Futabatei Shimei’s translation in the Japanese magazine Kyōmi. Second, the framed narrative and contrasting styles of Lu Xun’s short story, which are not features of Gogol’s, might also be due to the inspiration from the Japanese genbun itchi movement in the Meiji period. Third, and most importantly, cannibalism, a major theme in Lu Xun’s Diary of A Madman, was arguably shaped by the heated discussion in Japan on national character and cannibalism. My paper will trace the double origin of the depiction of madness and cannibalism in Lu Xun’s work and illustrate the importance of the role of Japan in the transculturation of the story of a madman.